This invention relates to electric motors and similar electric machines, and more particularly to a stator with winding coils suitable for automatic fabrication and insertion and to a method of manufacturing such a stator core and winding assembly.
Stator wound motors including the widely used ac induction motor with a squirrel cage rotor at present are constructed with pre-formed and insulated closed loop stator coils that are inserted manually into the stator slots and connected together to form the winding. The common insulation-wrapped stator coils require semi-manual and manual operations for their fabrication, especially as to forming the wound coils to shape, wrapping or taping with insulation, and insertion. Since the coil is wound in a closed loop, automatic mechanisms to wrap the wires with insulation are extremely complex and not always economical or technically practical. Insulation prior to forming the coils is already provided on the individual wires but insulation around the group of wires that form the coil is also necessary. This latter insulation operation is not possible before coil forming because it would require increased flexibility to the point where forming would not be possible without marring the insulation. Hence, manufacturers are forced to their present process technique. Further, the slot gaps in the stator core through which the wrapped coil sides are forced during assembly to the stator core are desirably small for improved electrical performance making it difficult to insert the coils. Automation of the insertion process is possible for some small motors but even then many hand operations are still required to tie end turns, adjust the shape, insulate and join consecutive coils. What little automation is done is achieved through specialized machines with tooling unique to the motor size. The forming and insulation of stator coils and insertion into stator slots accordingly is the most labor intensive area in the manufacture of electric motors.